Most tropical hibiscus you find at the store are the
common "garden varieties" and were propagated by rooting
cuttings. Some varieties are easier than others to root.
Many growers use a perlite rooting medium in plastic pots.
Using a rooting hormone usually helps and it is very
important never to let the medium dry out. Putting 15 or 20
cuttings in a 6" pot is common and, depending on temperature
and lighting conditions, these may root in 6 to 8 weeks.
Warm temperatures, high humidity and adequate light are
important. Air-layering is also used for propagation.

Hybrids are usually grafted to rootstock varieties that have
proven themselves to be resistant to soil borne problems and
have a strong root system. Hybrids may or may not root
easily and their root systems may or may not be vigorous.
Every year there are new hybrids and the most effective way
to get these new varieties to the public is to graft.
To graft, a sharp knife is used to notch the rootstock and
expose the cambium layer below the bark. A sliver of the
hybrid with an "eye" is trimmed to expose its cambium layer
and inserted into the notch to match-up with the cambium
layer of the rootstock. This area is then wrapped with a
rubber strip to keep tight and then sealed with grafting
wax. To see a pictorial explanation, please visit this
excellent Australian
site. After viewing the Australian site, a slight
variation can be seen here.

Raising hibiscus from seeds is another means of propagation.
This is how new varieties are developed. When pollen is
applied to the female pads and a pod forms, it is usually a
couple of months until the pod ripens and exposes its seeds.
For a fuller discussion, please go to these pages on raising
from seeds and Buddy Pollinates. Getting
a pod to form on a plant can be very difficult --
60-80F degrees, high humidity and
"willing" parents. After the seeds have germinated and been
raised to maturity, 6 to 18 months, they will produce a
flower (and bush) with qualities from both the pollen and
the pod parent. Some of these flowers may be spectacular and
some may be inferior to their parents. The flower produced
by that seedling is genetically unique and until rooted or
grafted is the only plant capable of producing that
particular flower.